Bang gears for less....Multispeed for engine!

[MtnGoat]

Standarized jackshaft for NuVinci

Thanks Myron and Zomby Builder. Now I've got it clear in my mind, how those bearing hangers/washers work. I'm thinking these might be replaced by the bracket that attaches to the bike frame, using the same sized hole to attach to the bearing.

Zomby Builder, do you think it is necessary to double the bearings for a typical MB jackshaft? Or was that something specific to that one project?

Myron, I'm already comfortable calculating the gear reduction values, due to reading some of your previous posts on the subject. Thanks for getting me up to speed on that score. And you didn't even know you had! Like I said I've been scouring the forum for any information I can find about jackshafts.

Andrew was hoping to find or develop a standarized jackshaft for the purpose of easily using the NuVinci hub in mb applications. Getting in the right range might be difficult when using the NuVinci hub off a single jackshaft that moves the drive to the right. The usual Happy Time setup reduces an additional approx 4 to 1 by going from the drive sprocket to driven sprocket on the wheel. 4 to 1 makes for a pretty big sprocket on the jackshaft if one can't get any additional gear reduction going from the jackshaft to the NuVinci hub. Seems Staton is using a 36 tooth driven sprocket on the NuVinci hub, AFTER already reducing the ratio to 18.75 to 1 in his gear box. I don't understand why such a big 36 sprocket is appropriate, but I'm sure he's got it calculated correctly.

The NuVinci at $250-300 with sprocket would be quite attractive. My only reservation is the weight, assuming I could work out the gear reduction and right side drive issues cost effectively.

 

[5-7HEAVEN]

MtnGoat, you're welcome. A few builders here have welded an extra crankset bracket into the frame. There are special components to convert it into a very strong(but not adjustable) jackshaft.

When most people consider using the NuVinci hub, they fail to take into consideration that David Staton is using this hub in conjunction with his gear chain drive gearbox.

There is an 18.75:1 gear reduction BEFORE it links with the NuVinci hub. The hub does not openly advertise what its gearing is. HOWEVER, through some speed/rpm stats advertised on STATON'S website, one can calculate what the NuVinci hub's gear reduction range actually is.

You'll be surprised.

Dave starts with a 26" bicycle, using a 22t drive sprocket on his gearbox and a 36t on the NuVinci hub.

At 7,000rpm, maximum speed is 9.49 mph in lowest NuVinci gear.

This computes to a low drive ratio of 58.7:1 final drive, as compared to happy time engine with 143t sprocket.

At 7,000rpm, maximum speed is 32.9 mph in highest NuVinci gear.

This computes to a high gear drive of 16.87:1, as compared to happy time's engine with 41t sprocket.

Therefore, the NuVinci hub has gear spacing of a LOW 1.913:1 and a HIGH of .55:1.

Any enthusiast thinking about installing this hub should realize that they need to factor in some MAJOR gear reduction at the jackshafts...

ORRR design the STATON gearbox into their drivetrain.

Here's what would happen if you linked the NuVinci hub directly with your happy time engine. This is with NO gear reduction at the jackshaft(10t sprockets on both ends):

At 7,000 rpm, maximum speed is 19.72 mph in lowest NuVinci gear.

This computes to low drive ratio of 28.24:1,as compared to happy time engine and 69t sprocket.

At 7,000 rpm, maximum speed is 68.6 mph in highest NuVinci gear.

This computes to a high gear drive of 8.12:1, as compared to happy time engine and 20t sprocket.

At first glance, one might say that the NuVinci hub MIGHT work with a direct happy time connection. HOWEVER, one would not be using the intermediate and high gear to its fullest advantage. This is especially true if you run an 8500rpm MITSUBISHI or an 11,500 rpm pocket bike or chainsaw engine.

Hope this helps prevent a few expensive nightmares.

Myron

 

[andyinchville1]

Hmmm...Actually it may be GOOD to run the HT without a lot of reduction prior to going into the NuVinci...reason being there is a lot of twisting that must go on at the controller for the hub to go from one extreme to the other (the hub is shifted by rotating a twist grip type control....If we only have to use a little bit of travel to cover the wide range you mentioned I think we'd be set.....I mean a 20T to 69T sounds like all the range I'd ever want.....I heard that HT engines on a single sprocket shouldn't go much below 32T anyways...BUT 20 T on a down hill with full throttle....wow!

As far as cost....If we can get a good easy to attach jackshaft...we'd have the multipeed tranny issue almost licked because I can get us NuVinci's for about $275 delivered to your door in the lower 48 .....We are just soooooo close!

 

[5-7HEAVEN]

Hmmm, Andy, I guess someone here will do it, sooner or later.

Myron

 

[Zomby Builder]

HMMMM might be me!!

OK you could probably get away with only using one bearing on each side. I do this because you see all the sprockets are on the right side. I tryed this red bike set up with nothing but the bottom bracket bearings. No hangars. It looked real clean & worked great for 50 miles. Then the shaft chewed up the right hand bearing. Too much cantlever on the shaft. If you had the driver on the left it may be OK. I would still use one hanger on each side as well as two additional bearings inside the bottom brackets for a left handed driver. I am wanting to do this with a Whizzer motor. As soon as the Whizzer motor can be started with the new electric start I will. So count me in on the discounted NuVinci. This setup should have awesome torque with a 22 tooth driver on the left & the smallest possible reduction sprocket on the right, and a 22 tooth on the NuVinci. You could do this now with a happy time, I just want a higher quality motor. Why spend the time and $$$$ doing this with a $100 motor???

If you want an inexpensive jackshaft: just weld those hangers on each side of a stock bottom bracket. It would be an easy weld that any amateaur welder could do. Then just weld in the bottom bracket into your frame. Use the bearings that come in the kit & drive it on the left reduce it on the right & ROCK ON DUDE. Just put the bearings so that the short side faces your drivers.

 

[MtnGoat]

Staton - NuVinci gear reduction

Myron, check my math and inputs, since it doesn't match yours. NuVinci hub range from their website is 0.5 - 1.75.

Staton set up highest gear:
18.75 * (36 nv sprocket / 22 Staton drv spkt) * (.5 nuvinci H reduction) = 15.34 to 1
You have 16.87 to 1

Staton set up lowest gear:
18.75 * (36 nv sprocket / 22 Staton drv spkt) * (1.75 nuvinci H reduction) = 53.69
Your value was 58.7 to 1

Where are we differing? I want to make sure I'm doing this correctly.

 

[5-7HEAVEN]

MtnGoat, I'm using .55:1 instead of .5:1, utilizing the stats taken off STATON'S site.

I'm also using 1.913:1 instead of 1.75:1 for the same reason.

That computes to +.88(to 10.37 mph) in low gear, and +3.4(to 36.3 mph) on the high end.

The proof will be in the actual experiment, not our theoretical calculations.

Myron

 

[MtnGoat]

It's good to know I've got the method right. That's what I wanted to check. I get the same reductions you do when I put in the Staton site numbers.

 

[Zomby Builder]

Method??

Please fill me in with how these numbers relate to my boney arse. With a bike that weighs conservatively 100 lbs. With a 200 elbo rider.. You guys make this sound like an equation that is real. Are you considering HP?? Or just gear reduction?

 

[5-7HEAVEN]

Zomby, gear reduction is an important factor. It helps calculate rpm at mph, and are general theoretical calculations. It becomes more specific when the rider's engine's HP and torque ranges are known.

Total weight, wind resistance, friction losses from all aspects will detract from these mathematical calculations.

They are simply ballpark figures. They show if you're within your engine's power range, or 'way out in left field.

Myron